The present invention relates to electrical and electronic components, and pertains particularly to an improved compliant surface mount lead for electrical and electronic components.
For many years, electronic circuit boards have been fabricated by interconnecting a plurality of electronic components, both active and passive, on a planar printed circuit (PC) board. Typically, this printed circuit board has comprised an Epoxy/fiberglass laminate substrate clad with a sheet of copper, which has been etched to delineate the conductive paths. Holes were drilled through terminal portions of the conductive paths for receiving electronic component leads, which were subsequently soldered thereto.
More recently, so-called surface mount technology has evolved to permit more efficient automatic mass production of circuit boards with higher component densities. With this approach, certain packaged components are automatically placed at preselected locations on top of a printed circuit board, so that their leads are registered with, and lie on top of corresponding solder pads of the conductive paths. The printed circuit board is then processed by exposure to infrared or vapor phase soldering techniques to re-flow the solder, and thereby establish a permanent electrical connection between the leads and their corresponding conductive paths on the printed circuit board.
The increasing miniaturization of electrical and electronic elements and high density mounting thereof has created increasing problems with electrical isolation and mechanical interconnection. In particular, it creates more difficulty establishing reliable and efficient connection between packaged component lead terminals and PC boards. Presently known interconnect methods severely limit the ability to provide density and reliable electrical and mechanical connection between terminal points and PC boards.
Another problem of the present state of the art is that there is often a mismatch between the coefficients of thermal expansion of components and printed circuit boards. This often results in fatigue failure of the lead attachment to the PC board.
Among the electrical and electronic elements that must be surface mounted on PC boards are bi-filar wound cores used as inductors in circuits. These are preferably connected through some form of header or packaging with suitable terminals. The current technique of surface mounting of these and other similar components is by separate component lead terminals. Recent improvements have been made, such as disclosed in U.S Pat. No. 5,015,981, issued May 14, 1991 to Lint et al, and U.S Pat. No. 5,032,953, issued Jul. 16, 1991 to Carl et al, both assigned to the assignee hereof. These current techniques of mounting are time consuming, difficult to machine assemble, and frequently result in reliability problems.
It is, therefore, desirable that an improved more reliable attachment of electronic components to PC boards be available.